The present invention relates to a pump device applied to, for instance, a hydraulic power steering device of a vehicle.
As is well known, a pump device is provided with a relief valve for protecting hydraulic devices from an excessive pressure increase. This relief valve has a structure in which a spherical valve body held by a valve body holding portion of a retainer is forced or pressed to a valve seat side by a coil spring. However, the relief valve has a problem of generating noise caused by the fact that the valve body vibrates by working fluid flowing on a surface of the valve body at valve opening.
To avoid this problem, Japanese Unexamined Patent Application Publication No. 2012-082762 (hereinafter is referred to as “JP2012-082762”) discloses a technique that suppresses the noise caused by the vibration by employing the following structure; a valve seat portion on which the valve body is seated during closure of the relief valve is offset to a radial direction one side with respect to a bore center of a relief valve accommodation bore that accommodates therein the relief valve, and thus a pressing force according to a hydraulic pressure acting on the valve body has a radial direction component to the radial direction one side. That is, since the valve body is held at the radial direction one side with stability during opening of the relief valve, the vibration is suppressed, then the noise caused by the vibration is suppressed.